Your car won't start if your timing chain has snapped. You'll need to remove the valve cover to inspect this. You'll also need to know what to look for when we're dealing with worn gears or chain. if it has snapped you won't have to worry about it because the guy would have had an extensive expense to repair the car and make it work again. These chains and gears typically don't wear out if the oil level is up and changes were done regularly. The timing chain tensioner - hydrolic - starts to give after a few hundred thous km. makes a clanking noise in the timing case. These are about 100.00 and easy to replace. The timing chain guides sometimes wear out too if not taken care of this is more extensive and requires you to go into the motor to change.